1. Field of the Invention
The present invention is generally directed to an apparatus and method for intermittent manufacturing and storing nitrogen gas, separated from air, using a permeable membrane in a compact, automatic, and unattended process. The nitrogen may be used in product manufacturing processes, inflating tires, vending to customers for tire inflation, filling portable nitrogen vessels, and other applications by people needing nitrogen.
2. Description of the Prior Art
Nitrogen manufacture from air by separating the oxygen and nitrogen has been accomplished by selective absorbent materials, distillation of liquid air, and membrane separation. These processes produce nitrogen for industrial uses such as chemical manufacture, inert gas welding, purging of explosive environments prior to electric arc cutting or welding, and food preservation. Also these processes are mostly continuous nitrogen production to the industrial process or to continually fill large storage containers. U.S. Pat. Nos. 5,302,189; 5,004,482; 4,810,265; 4,348,213; and 3,140,931 describe these manufacturing processes and industrial uses. The absorbent materials, although efficient, require regeneration of absorbent materials.
U.S. Pat. No. 5,388,413 describes a portable nitrogen source for continuously producing nitrogen at various sites with flow rates controlled by restrictor assembly (item 60, col. 3 line 67) adjusted manually to control operation. This patent uses a membrane for gas separation with air cooling and then air heating to provide proper temperatures to control the membrane temperature for gas separation. Although these provisions may be sufficient for continuous generation of nitrogen gas, the patent is not adequate to provide proper separation on start up or intermittent operation. Pressure controls are manually adjusted and temperatures are inadequate for proper gas separation until steady state production of nitrogen occurs. For intermittent and unattended production, immediate separation of nitrogen from air is needed when starting or oxygen will dilute the nitrogen. The prior art processes also require operators to produce the nitrogen gas.
U.S. Pat. Nos. 4,452,341; 4,289,225; 4,236,622; 3,208,574; and 1,427,529 relate to the intermittent supply of air. These patents supply air for inflating tires.
Publications such as Goodyear Application Bulletin no. 17 (09-85), Longer Tires, (01-95) describe the advantages of using nitrogen rather than air for safety, longer life, and therefore less cost. However, there is no system found in the prior art that provides compact, intermittent, and automatic production of essentially pure nitrogen for manufacturing, consumers, or tire inflation.